Apparatus for making thermoplastic joints



Nov. 20, 1945,` R. lN. s'rEFFENs 2,389,560` APPARATUS FOR MAKING THERMOPLASTIC JOINTS original Filed March 2e, 1942 A I le, F167. y I Im/ENTOR. n

RO B ERT N. 51E FF ENS Patented Nov. 20, 1945 APPARATUS FOR MAKING THERMOPLASTIC JOINTS y Robert N. Steffens, New York, N. Y.

Original application March 26, 1942, SerialNo. 436,256. Divided and kthis application November 2, 1943, Serial No. 508,725

s claims. (o1. 154-42) This invention relates to apparatus for making thermoplastic joints, particularly for joining strips of thermoplastic material, or the endsA of a strip of such material to produce a belt of uniform thickness. This application is a division of my co-pending application Serial No. 436,256,`

illed March 26, 1942, for Methods of and apparatus for making thermoplastic Joints. issued as Patent No. 2,379,500, dated July 3. 194.5.

An object of this invention is to provide ahighly improved apparatus of the character described, for joining meeting ends of strips of thermoplastic material, or the ends of a strip of such material to make a belt, without any overlapping oi material at the joint, and so that the material at the Joint is of uniform thickness with the remainder ofthe strip or belt.

Onefapplication of the improved apparatus is forming endless die wiping belts for die stamping presses used for imprinting from intaglio engraved plates and dies, the belts serving to remove surplus in4 from the plate or die surface. The constructV of die stamping presses prohibits installationjof pre-formed endless wiping belts into the pressi; For this reason, the strip of wiping material must be threaded through the various parts of the pressand the ends yof the belt must then be attached together, so as to form an endless belt. The present improved process is particularly applicable for attaching the ends of a wiping belt made of thermoplastic material such as Plioillmf viny1 resin, Vinylite," Koroseal," or the like thermoplastic sheets.

Another object of this invention is to provide an improved apparatus -of the character` described, which may `be easily manipulated, and which shall be inexpensive to construct and economical to operate, and which may be used for joining together the ends of a ystrip of` thermoplastic-material threaded through the mechanisms of a die stampingpress to join the ends of the strip `together for lproducing an endless belt 'ci uniform thickness throughout, without any increase in thickness or bumps at the joint.

Other objects of this invention will" in part be obvious and in part hereinafter pointed out.

The invention accordingly consists in thefeaturesof construction, combinations of elements, and arrangement of parts which will be exempliiled in the construction hereinafter described, and of which the scope of application will be indicated in the following claims.

In the accompanying drawing in which is shown one oi' the various possible illustrative embodiments of this invention,

Fig. 1 is a. top Aplane view of apparatus embodying the invention;

Fig. 2 is a cross-sectional view taken on line 2-2 of Fig. 1';

Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. l; Fig. 4 is a partial view similar to Fig. 3, and

illustrating another step in the process;

Fig. 5 is a View similar to Fig. 4, and illustrating still a further step in the process;

Fig.'6 is a view similar to Fig. 5, and illustrating the clamps loosened and separated after the strip ends are Joined together to form a belt;

Fig. 7 is a top plan view of the structure shown in Fig. 6; and

Fig, 8 is a side` elevational view of apparatus embodying the invention, and illustratinga modiiied construction.

Referring now in detail to the drawing, III designates a clamp forming part of the apparatus embodying the invention, `for joining together the ends II and I2 of a strip or strips I 8 of thermoplastic material. 'I'he ends II and I2 may be the ends of a single strip, or the ends of a pair of strips of thermoplastic material. The thermoplastic material may be viny1 resin, Vinylite, Korose'aL Pliofilm," or the like thermoplastic material.

The clamp I0 comprises a guide member I4 having a. bottom wall I5, and parallel, upstanding guide ilanges I6. On the guide Il is a xed clamp I1 and a slidable clamp I8. Fixed clamp I1 comprises a pair of substantially similar, symmetrically disposed iaws or clamp plates I8 and 28. The clamp plates I9 and 28 have a width equal to the distance between the ilanges I8. Said plates have horizontal top and bottom surfaces and may be of substantially similar thickness.

The bottom plate I9 may be xed tothe guide Il by screws 2| screwed through vertical threaded openings 22 in the bottom wall I5, and through threaded openings 28 in the underside of plate I9, registering-with' the openings 22. 'I'he openings 22 and 23 are located adjacent the anges I 8. Plate I9 is furthermore formed on the underside thereof wltha pair of countersunk sockets 28, located in alignment with the threaded openings 28. Said plate i8 is furthermore formed with vertical through openings 26, communicating with the sockets 25.

The upper jaw plate 20 is formed with ver- `tical through openings 28, registering with the openings 26. Extending through the registering openings 28 and 28, are bolts 28 having heads locatedfwithin the countersunk sockets 25. Nuts are screwed to the upper ends of the bolts 29, to press the plates I9 and 20 together.

It will be noted that one of the strips I3 is placed between the clamp jaws I9 and 20, with the end II of the strip projecting beyond the operating ends of said jaws. It will be noted furthermore, as illustrated in the drawing, that the forward ends of the plates I9 and 20 are inclined rearwardly and outwardly, as at I9a and 20a, for the purpose hereinafter appearing.

The sliding clamp I8 comprises a bottom jaw plate 32 and a top jaw plate 33 of the same width as the jaw plates I9 and 20. The clamp I8 is adapted to slide between the guide flanges I6, as shown in the drawing. Said jaw plates 32 and 33 are preferably of equal thickness, and similar to the thickness of the jaw plates I9 and 20.

The jaw plate 32 has countersunk sockets 34 on the underside thereof and is formed with vertical through openings 35. Each plate 33 is formed with vertical through openings 36, registering with the through openings 35. Extending through the through openings 35, 36, are bolts 31 having heads disposed within the sockets 34. Nuts are screwed to the upper end of the bolts to press the plates 32 and 33 together. The bolts 31 are spaced apart similarly to the bolts 39, so as to be disposed on opposite sides of the strip I3 which is received between the plates 32 and 33.

It 4will be noted thatlthe forward end I2 of strip I3, gripped by theclamp I8, likewise projects beyond the inner ends of the jaw plates 32, 33. It will be noted furthermore that the forward ends of said jaw plates are inclined rearwardly and outwardly, as at 32a and 33a, similarly to the inclination of the surfaces I9a, 20a.

The operation of the apparatus t join together the meeting ends of the strips I3 will now be explained.

The two ends of the thermoplastic strips are firmly held by the clamps l1 and I8, with the inner ends of the strips projecting beyond the knife or shearing edges Aof the clamps'. The projecting ends of the thermoplastic material are trimmed off against the leading edges of the clamps to square oil' the edges. The clamps are then loosened and more material is exposed and the clamps are then again tightened.

Clamp I8 is then moved towards clamp I1. However, a chromium plate or stainless steel blade or knife 40 heated to about 350 F. is interposed between the meeting ends of the strips, as illustrated in Fig. 4 of the drawing, so that the ends of the strips contact the opposite surfaces of the hot blade or strip of metal indicated by numeral 40 in the drawing.

Preferably about 1A, of an inch of thermoplastic material projects from the inner endsof the two strips. The sliding clamp is then pressed toward fixed clamp I1 causing the protruding ends of the strips to press against opposite sides of the blade and become heated and plastic and soft. The hot blade 40 is then withdrawn and clamp I8 is moved further toward clamp I1 to the position shown in Fig. to cause the plastic ends of the strips to meet and be pressed together so that they will become fused.

At the same time, the jaws ISb and 20h' at the inner ends of the surfaces I9a, 20a, practically contact or do contact, the jaws 32h, 33h at the inner ends of the surfaces 32a, 33a, respectively, to smooth out the joint and make the joined portion of the strips of uniform cross-sec tion. Excess material will'be squeeze up and,

down into the V-shaped grooves formed between the surfaces a, 33a and I9a, 32a. These strips will be joined to the belt by a narrow neck and can be easily stripped ofi', or will be sheared oil.' by the edges of the clamps.

The thermoplastic material will not become attached to the chromium plated or stainless steel hot blade. The portions of the clamps close to the heated edge are also preferably chromium plated, so that the plastic material will not adhere thereto. After the joint is formed bolts 31 may be loosened and clamp I8 may be moved back. The two clamps may then be opened up by withdrawing the nuts on the bolts 29 and 31.

It will thus be seen that there is formed a smooth butt joint edge to edge, and that the thickness of thel joint is the same as the thickness of the strip or strips.

In Fig. 8 there is shown apparatus Illa embodying the invention and illustrating a modified construction. 'I'he apparatus Ilia comprises a pair of clamps 40 and 4I. Clamp 40 comprises a pair of similar, symmetrically disposed, clamping jaws 42. Each clamping jaw 42 comprises a thin knife blade 43 attached to or backed by a metal plate 44.

Clamp 4I comprises a pair of similar, symmetrically disposed jaws 45. IEach jaw 45 comprises a knife blade 46 fixed to a backing plate 41. The knife blades 46 also extend beyond the backing plates. The jaws of each clamp may be attached together by screwssimilar to the screws 29 and 31 of Fig. 1. One of the jaws 42 of clamp 40 is attached to a rod 48. One jaw 45 of clamp 4I is attached to rod 49 pivoted to rod 48, as at 50. The clamps are on equal radii so that upon swinging rods 48 and 49 about their common hinge 50, the clamps will be brought together.

The strips I3 of thermoplastic material are gripped in the clamps and the meeting edges are brought into abutting relation by swinging the rods 48 and 49 relative ,to one another. The method of carrying out the process of forming a 45 butt Joint is similar to that described above for `aparatus I0.

It will be noted that the edges of the clamps in apparatus I0 or Illa, adjacent to the thermoplastic material are shaped in such a way that the meeting edges of each clamp form approximate knife or shearing edges, with the body portion of the clamp relieved either by the formation of an acute angle or any other means. 'I'his construction results in a shearing pressure at the joining joint of the thermoplastic material, and also provides anarea into which surplus material can readily flow.

It will be noted that the jaws may either be co-planar or swung about equal radii, it being a dominant feature of the invention that the jaws are so associated that relative movement therebetween will cause the inner edges of the thermoplastic strips to meet in abutting relation whereby to form a butt joint.

It will thus be seen that there is provided a device in which the several objects of this invention are achieved and which is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention. and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

2,389,560 Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. Apparatus for joining together end portions of flat thermoplastic strips, comprising a pair of clamps, each clamp having means to grip an end portion of sheet thermoplastic material, and means -to-support said clamps for relative movement to bring one end portion into edge to edge contact with the other end portion. each of said clamps comprising a pair of jaws having parallel flat clampingy surfaces adapted to contact opposite surfaces of one of said strips, the inner ends of the jaws of each clamp having shearing means at said clamping surfaces and being relieved from said clamping surfaces, beyond said shearing means to provide space to receive surplus sheared material.

2. Apparatus for joining together end portions of flat thermoplastic strips, a guide having a pair of lclamps therein, each clamp having means to grip an end portion of sheet thermoplastic material, means to support said clamps for relative movementto bring one end portion into edge to edge contact with the other end portion, each of said clamps comprising a pair of jaws having parallel nat clamping surfaces adapted to contact opposite surfaces of one of said strips, the inner ends of the jaws of each clamp having `shearing means' at said clamping surfaces and being relieved from said clamping surfaces, beyond said shearing means to provide space to receive surplus sheared material, means to attach a jaw of one clamp to said guide, means for pressing together the jaws of each clamp, said other clamp being slidably mounted in said guide.

3. Apparatus for joining together end portions of flat thermoplastic strips, a guide having a pair of clamps therein, each clamp having means to grip an end portion of sheet thermoplastic material, means toasupport said clamps for relative movement to bring one end portion into edge to edge contact with the other end portion, each of said clamps comprising a pair of jaws having parallel iiat clamping surfaces adapted to contact opposite surfaces of one of said strips, the inner ends of the jaws of each clamp having shearing means at said clamping surfaces and being relieved from said clamping surfaces, beyond said shearing means to provide space to receive surplus sheared material. means to attach a jaw of one clamp to said guide, means for pressing together the jaws of each clamp, said other clamp being slidably mounted in said guide, said guide having parallel guide flanges slidably engaging opposite sides of the second clamp.

ROBERT N. STEFFENS. 

